Hi, I do the commute everyday and it is doable, it takes me 2 hours door to door from Bensville to Woy Woy Station to the CBD, terrigal would take a bit longer as you would need to go to Gosford. If you were working in Ryde you would get the Strathfield train and change at McQuarie Park, the train during would take about 1hr 15...you can check timings and the best way to go by going on 131500 website which is the transport website. Chatswood would be better as that takes just under an hour.
for the lifestye on the coast it is worth it, I usually work on the train and have that time taken into account for my working day. The trains are nice and quiet. I would not reccommend driving, the roads can be really busy and parking is a nightmare